Treating hydrocarbons



Jan. 8, 1946. J. R. scHoNBr-:RG ET Ai. 2,392,773

TREATING HYDRocARBONs Filed Dec. 27, 1940 w www@ H N .QN

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Patented s, 1946 UNITED STATES 2.392.713 l 'rename maocsanons Jackson n. schouten, Westfield, yma Harold J. Moyer, Summit, N. J.,asaig'nors to Standard Oil Development Com Delaware pany, a corporation of Application December v27, V19.40, Serial No. 371,898

3 Claims. The present invention'relates to improvements 4in the art of treating hydrocarbons, and, more particularly, to the art of preparing or conditioning a feed stock for a catalytic cracking operation so that when the stock is cracked catalyti- 8 cally it will produce greater yields of gasoline of high anti-knock quality, without forming excessive amounts of coke, and be otherwise more desirable for catalytic cracking than would be possible without benefit of methods herein dis- 10 closed.

It has long been known that a cracking stock comprising mostly parainic hydrocarbons is the most desirable one to subject to thermal cracking to produce high yields of gasoline while at the l5 same time maintaining satisfactory operating conditions, and without excessive formation of undesirable by-products such as gas and coke. It`

vis known further, that as the parailinicity of cracking stocks decreases the yields of gasoline attainable by thermal cracking also decrease,

while the undesirable products of decomposition and the severity of operating conditions to obtain decomposition are relatively increased.

In the catalytic cracking of petroleum oils,

however, it has been found that stocks of the highest content of paraiiinic hydrocarbons are not the most desirable when judged by gasoline yields, relative production of the undesirable products, and conditions of operation.

We have discovered that better yields oi.' high quality gasoline can be secured from catalyticfeed stocks in which the degree of unsaturation and cyclization .isor has been caused to be-high,

than from stocks in which parafinic hydrocarbons predominate. t

Since gas oils which are basic materials for Y cracking operations vary widely in their hydrocarbon composition due both to origin and boiling range, the desirability 'of conditioning a-specinc 4 stock for catalytic cracking in -the manner we propose is dependent on its composition. That is, if a virgin stock is predominantly parafnic, it is. less susceptible to catalytic cracking reactions than a stock predominantly naphthenic, and should be conditioned in a manner to remove or convert paralns, or conversely, to increase the concentration of olefinic and naphthenic hydrocarbons, in order to improve the catalytic cracking yields and operation. If, however, the stock 50 to be catalytically cracked is largely naphthenic in character, then the proposed conditioning is not economical or advisable.

The object of our invention is to reduce the paramnicity of such petroleum fractions as are predominantly parafiinic in character, by means v oi'thermal cracking and other pyrolytic decomposition such as cokingof petroleum residues, for the purpose of preparing and selecting a gas oil charge stock for catalytic cracking which is more 60,

ject the oil` fraction to intensive pyrolysis. In

fact, severe thermal cracking is avoided in order tokminimize the production of gasoline and gaseous hydrocarbons. The object of the pretreatment is primarily that of reducing parailinic hydrocarbons to4 naphthenes and oieiins. and for this purpose advantage is taken of the greater reactivity of parailins to decompose under thermal conditions than are the hydrocarbons of other types.

The thermal pretreatment is applicable to gas oils, reduced crude oils and crude pitch residues. Such products as crude pitch, high-boiling cracked tar. and other petroleum residues may also be coked. In both of these pyrolytic proces ses, the gas oil product is then subjected to catalytic cracking. This procedure differs from present methods of cracking wherein the products of distillation of the crude oil, without cracking, are subjected directly to the catalytic cracking reactions.

The principle embodied in our invention is not limited vto use on gas oils or other stocks of highboiling character. It can be appliedalso to the cracking'of gasoline fractions, when it is desirous to improve the octane number of this product. D

-Sumatran reduced crude having the followingr inspection Gravity, A. P. I 21.5 Initial boiling point-"F 454 5% at, F 1 725 10% at, F 760 20% at, F. 815 30% at, F o `84'? at, F 8"!5 Per cent ofiat 900 F 48 Sulfur; 0.15

5 Furolviscosity at 140 F 26.1

is introduced into the system through line i and thence discharged into a coil 3 disposed in a furnace setting 4. in which coil it is heated to a temperature of 870 F. and thereafter withdrawn through line 6 and discharged into a drum reactor drawn through line I and discharged into a fractionating column I2. In fractionating co1- uxnn I2,V the following fractions are removed: Through line I4 13.7 volume per cent based on the original charging oil of 400 F. final boiling point gasoline, and 2.7 by weight per cent of normally gaseous hydrocarbons are withdrawn. About 65 volume per cent of gas oil having an A. P. I.

gravity of 28.1 is withdrawn from'f tower I2,

through line I8. From the bottom of tower I2, through line I6 21.4 volume per cent of pitch Dommia-having an A. P. I. gravity of 4.8 are withdrawn. In drum 8 0.9 per cent by weight of coke is formed as a result of the pyrolysis which takes place. i

The pitch bottoms ortar withdrawn through line I8 are fed to a continuously operated coking drum I9. The pitch bottoms in the run, as stated, have anl A. P. I. gravity of 4.8, a furol viscosity of 225.5 at 210 F., a sulfur percentage by weight of 0.18, a softening point of 123 F., and a'Conradson carbon content of 23.8%. This material was, after preheating in furnace I1, continuously fed to the coking drum I9 where it was subjected to the following operating conditions: namely, an inlet temperature of 885 F., and outlet temperature of 788 F., a pressure ci' 50y lbs/sq. in. gauge being maintained in the drum or by other suitable means. products were withdrawn from drum I9 through line 3| and discharged into a iractionating eolumn 33. From fractionating column 33 5.5 per cent by weight of normally gaseous hydrocarbons, and 12.8 per cent by volume of 400 F. end point gasoline were withdrawn overhead through line 35, 55.5 per cent by volume of gas oil having an A. P. I. gravityI oi.' 20.1 was withdrawn from the column 33 through line 36, and this material was discharged into line I8 where it mixed with the gas oil obtained from fractionating column I2. The mixed fraction fed to coil had the following inspection:

Gravity. A. P.I 26.9

Initial boiling point, F 440 50% o5 at, .F 750 .90% ot! at. F 920 Anilino point, 185

This material was heated in coil 20 of furnace 2I to a temperature of 906 F., whereupon it was Y withdrawn from the coil and mixed with a powdered catalyst in an injection means 22 or other suitable mixing device, the amount of catalyst being 2.14 parts by weight of catalyst to 1 part by weight of oil. The catalyst may bean acid treated clay, and preferably in powdered form, having a particle size within the range of from 20G-400 mesh. 'I'he catalyst may be stored in a receptacle from which it may be withdrawn through transfer line 21 and discharged into injection means 22, as indicated. The suspension of catalyst in the oil vapors is then withdrawn from injection means 22 through line 24 and discharged into the bottom of a reaction chamber` 2l where, under the conditions stated, the vapors remain for a period of 10.8 seconds, and under a pressure oi about lbs/sq. in. gauge. In reactor 26 the gas oil undergoes conversion forming 40 per cent by volume of gasoline having a iinal boiling point of 400 F. The reaction vapors are withdrawn through reactor 26 through line 28 and discharged into a second fractionating column 30. From fractionating column 30 5.5 per cent by weight of dry gas and 4.6 per centv by volume of butane, and 40 per cent by volume of gasoline were withdrawn overhead through line 40; 4.5 per cent by weight of coke was deposited on the catalyst in reaction chamber 26. Fiftytwo per cent by volume of gas oilwas withdrawn from fractionator 30 through line 42, this gas oil having an A. P. I. gravity of 24. This gas oill fraction was discharged into a furnace 45 in a coil 46 in which it was heated to reaction conditions as will subsequently appear. The material in line 42 had the following inspection:

Gravity, A. P. I 24.0 Initial boiling point, F 442 50% ofi` at, F 710 Final boiling point, F 900 into line 50 and thereafter discharged into a frac- I'he reaction tionator 52. From fractionator 52 8.4 per cent by weight of dry gas and 28 per cent by volume of 400 F. end point gasoline were withdrawn overhead through line 55: 63.8 per cent of tarry material having an A. P. I. gravity of 12 was withdrawn through line 51; 1.0 per cent by weight of coke was also produced in the reaction.

The specic example hereinbefore set forth is purely illustrative and does not constitute a limitation on our invention.

A variation of the procedure hereinabove set forth may be desirable when an examination of the thermally conditioned gas oil reveals experimentally that its several parts, obtained by distillation and separated according to boiling range, vary widely with respect to types of hydrocarbons composing each. Those fractions of the gas oil which contain mainly naphthenic, olenic and aromatic hydrocarbons are preferably next subjected to catalytic cracking, while those predominantly paraiiinic are recycled to the thermal con-v ditioning operation. To make such separation vby boiling range, suitable fractionation can be applied to the thermally cracked gas oils as produced.

Depending of course on the nature of the original chargingstock, the operating conditions in both thermal and catalytic cracking will vary;

. The gist of our invention, however, resides in the concept of first thermally treating or conditioning a charging stock in order to prepare a gas oil which will be suitable for catalytic cracking and recovering from the catalytic cracking operation a gas oil which is also thermally treated in order to condition or preparel it for further catalytic cracking. In the thermal cracking operationI v What we claim is: v

LThe method oi cracking which comprises subjecting a paramn base hydrocarbon oilv containing Vfractions of the gas oil boiling range to a thermal treatment at temperatures ranging from about 825". to about 1000 F.. pressures ranging from atmospheric to 1000 lbs/sq. in. and-for times of the order of 2 minutes, the exact conditions oi temperature pressure and treating time, being adapted to the speoiiic composition of said oil so as to causean increase of the naphthenicity of said oil without the formation oiv substantial amounts oi cracked gasoline and .saseous hydrocai-bons; recovering from the thermally treated products mostly-a gas oil tractionv of increased naphthenicityderived from parai'iinic hydrocarbons; and subjecting said recovered kas oil fraction to catalytic cracking.

2. The method of cracking which comprises passing a reduced paramn base crude oil containing fractions boiling in the gas oil range through i in 'said cil. recoverina (rein the products thus obtained mostly a sas oil fraction of increased nephtnenicity derived from paraiilnic hydrocarbons and subjecting said recovered gas oil fraction to catalytic cracking.

3. The 'method of `cracking which comprises passing a reduced paraiiin base crude oil containing fractions boiling in the gas oil range through cheating coil until the oil reaches a temperature f the order of 800 to 950 F., subjecting the preheated oil in a drum reactor to a thermal treatment at an average temperature in the range of 825 to 925 F., a pressure in 4the :range ci 0 to 200 lbs/sq. in. and for a time of the order of two ininutes to increase the amount of naphthenes, recovering from the products thus obtained mostly a g'as oil fraction of increased naphthenicity durived from paramnic hydrocarbons and subjecting said recovered sas oil traction to catalytic cracking with an acid treated clay catalyst at a teinperature in the range oi' 825 to 975 F. and under a pressure of 0 lbs/sq. in. sauge to 45 lbs/sq. in. gauge to obtain a high yield oi gasoline, and fractionating the catalytic cracking products separately from the thermal cracking products.

Jackson n. scHoNnm-to.-

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